If i have a 6.5 gallon pail, and a 5 gallon carboy... can i make two batches at once?

Yes--but you want to make sure you time it right so you're not rushing beer 1 in order to accomodate beer 2.

If you follow the 1-2-3 principle (1 week primary, 2 weeks secondary, 3 weeks bottle conditioning), then you can brew beer number two when beer number 1 has been in the secondary for a week. Then a week later, you bottle beer 1, clean and sanitize the carboy, and rack beer 2 into secondary.

On average, you can brew every two weeks with one primary and one secondary. If you get a second carboy secondary, you can brew (on average) once a week. This also gives you the advantage of being able to leave a batch in secondary longer than two weeks if it seems to need it, without it holding up the next batch.